A camera problem.

jenya7

According to https://doc.qt.io/qt-5/qcamera.html#State-enum :
In the active state as soon as camera is started the viewfinder displays video frames and the camera is ready for capture.
So capture should not be called right after start.
After calling start, you should asynchronously wait until the state turns to Active before performing any capturing.

so I did

void Camera::takeImage()
{
    m_camera->start();
    m_camera->searchAndLock();

     while (m_imageCapture->isReadyForCapture() == false) ;

    m_isCapturingImage = true;
    m_imageCapture->capture();

    m_camera->unlock();
}

it's never ready. never gets out of while.

SGaist

Hi,

Your tight loop does not allow Qt's event loop to run. You should either use an event loop to "block" the execution or properly implement this through signals and slots.

jenya7

@SGaist said in A camera problem.:

Hi,

Your tight loop does not allow Qt's event loop to run. You should either use an event loop to "block" the execution or properly implement this through signals and slots.

OK. Did so

connect(m_imageCapture.data(), &QCameraImageCapture::isReadyForCapture, this, &Camera::IsReadyForCapture);

void Camera::takeImage()
{
    m_camera->start();
    m_camera->searchAndLock();

   // while (m_imageCapture->isReadyForCapture() == false) ;

    //m_isCapturingImage = true;
    //m_imageCapture->capture();

    //m_camera->unlock();
}

void Camera::IsReadyForCapture()
{
    m_isCapturingImage = true;
    m_imageCapture->capture();

    m_camera->unlock();
}

It never happens.

JonB

@jenya7 said in A camera problem.:

connect(m_imageCapture.data(), &QCameraImageCapture::isReadyForCapture, this, &Camera::IsReadyForCapture);

Did this go through without complaint? I am "surprised", as QCameraImageCapture::isReadyForCapture() is not a signal, would have thought connect() would barf on that.... Try using void QCameraImageCapture::readyForCaptureChanged(bool ready) signal?

jenya7

@JonB said in A camera problem.:

@jenya7 said in A camera problem.:

connect(m_imageCapture.data(), &QCameraImageCapture::isReadyForCapture, this, &Camera::IsReadyForCapture);

Did this go through without complaint? I am "surprised", as QCameraImageCapture::isReadyForCapture() is not a signal, would have thought connect() would barf on that.... Try using void QCameraImageCapture::readyForCaptureChanged(bool ready) signal?

did so

connect(m_imageCapture.data(), &QCameraImageCapture::readyForCaptureChanged, this, &Camera::ReadyForCaptureChanged);

void Camera::takeImage()
{
    m_camera->start();
    m_camera->searchAndLock();
}

void Camera::ReadyForCaptureChanged(bool ready)
{
    m_isCapturingImage = true;
    m_imageCapture->capture();

    m_camera->unlock();
}

never get into ReadyForCaptureChanged

jsulm

@jenya7 said in A camera problem.:

never get into ReadyForCaptureChanged

Sure? How did you verify that?

jenya7

@jsulm said in A camera problem.:

@jenya7 said in A camera problem.:

never get into ReadyForCaptureChanged

Sure? How did you verify that?

I set a break point inside. I see it goes into takeImage but never gets to ReadyForCaptureChanged
Now I don't get any errors but it prints
Starting camera without viewfinder available
Is it OK?

J.Hilk

@jenya7
maybe its a typical object lifetime problem.

where does your Camera instance exist/live ?

JonB

@jenya7
Just to make sure, what happens in your code after you call your takeImage()? Do you allow the main event loop to run, or do you have other code which does not?

jenya7

@J-Hilk said in A camera problem.:

@jenya7
maybe its a typical object lifetime problem.

where does your Camera instance exist/live ?

It's a global object. I call it's methods from a command line parser object.

J.Hilk

@jenya7 soooo, inside main() ?

jenya7

@JonB said in A camera problem.:

@jenya7
Just to make sure, what happens in your code after you call your takeImage()? Do you allow the main event loop to run, or do you have other code which does not?

well..I guess it's running, cause my command lines parser reacts and process my commands.

jenya7

@J-Hilk said in A camera problem.:

@jenya7 soooo, inside main() ?

actually for debug purposes I instantiated it in other module - command line parser, but it's static and never goes out of scope.

J.Hilk

@jenya7

static

thats actually forbidden, no QObject based object must be created before the QCoreApplication instance. Static objects will be created before the QCoreApplication instance.

jenya7

@J-Hilk said in A camera problem.:

@jenya7

static

thats actually forbidden, no QObject based object must be created before the QCoreApplication instance. Static objects will be created before the QCoreApplication instance.

I mean it it's created without static attribute, but i's not locally allocated.

jenya7

If I only could drill down to the cause of
"Image Capture Error: Camera not ready"
What makes it not ready for m_imageCapture...

JonB

@jenya7
I know nothing about cameras and captures, so no idea about causes. I will say your definition of void Camera::ReadyForCaptureChanged(bool ready) is wrong, since it does not examine the ready parameter value. But if you say it's never hit that is moot.

jenya7

@JonB said in A camera problem.:

@jenya7
I know nothing about cameras and captures, so no idea about causes. I will say your definition of void Camera::ReadyForCaptureChanged(bool ready) is wrong, since it does not examine the ready parameter value. But if you say it's never hit that is moot.

Yes. But it never hits if (ready) line.

void Camera::ReadyForCaptureChanged(bool ready)
{
    if (ready)
    {
        m_isCapturingImage = true;
        m_imageCapture->capture();

        m_camera->unlock();
    }
}

J.Hilk

@jenya7
do you call show() on your viewfinder instance ? It will probably never change its state, if the viewfinder is not "visible"

JonB

@jenya7
Yes, at least the code is right, but won't help if that never gets hit.
Bearing in mind I know nothing about cameras, why did you comment out the m_camera->isCaptureModeSupported(...) lines, what do these actually return? If they return false presumably that would explain why you never get QCameraImageCapture::readyForCaptureChanged ?

Oh I see @J-Hilk has chimed in with some knowledge of this camera stuff....